For a porch light that is going to be left on all night, a 9 watt compact fluorescent lamp is normally adequate.

Affected by light pollution

If you are affected by intrusive light from your neighbour's property, discuss it with them and see if they can re-position the lights, so light is not directed at your property, or reduce the wattage to make the light less intrusive. If your neighbour is unwilling to co-operate, then contact Environmental Health & Licensing who will investigate.